Seamless of ERW steel pipe is divided into geometric seamless and physical seamless. Geometric seamless of ERW steel pipe is to remove the internal and external burrs.
Since the structure of the inner burr removal system and tool of continuous improvement and perfection, medium and large diameter steel pipe inside burr removal has been a good deal. Within the burr can be controlled in -0.2mm ~ + O.5mm so. Refers to the physical seamless weld microstructure inside, there is a difference between the base material and weld area resulting in decreased mechanical properties, the need to take measures to make it uniform and consistent technology. ERW steel pipe is for high-frequency welding thermal process and resulting in a temperature gradient, which is near the edge of tube and forming a molten zone, the semi-molten zone, overheating tissue, normalized area, areas not fully normalizing, tempering zones of the feature region. Which overheated zone tissue due to soldering temperature above 1000 ℃, the austenite grain grown dramatically in the cooling conditions will form a hard and brittle coarse crystalline phase, in addition to the presence of a temperature gradient will produce welding stress. Thus, the formation of the weld zone lower than the base metal mechanical properties of the situation is through physical seamless weld heat treatment process which uses local conventional induction heating device will weld area is heated to AC3 (927 ℃), then 60m length, the speed 20m / min during air cooling, water cooling when necessary. This method is used to achieve the elimination of stress, soften and refine the organization to improve the HAZ mechanical properties purposes. Currently, the world’s advanced ERW unit has been widely used for processing of the weld has obtained good results. Quality can not be argued that not only ERW pipe welds and weld coefficient of 1, the realization of regional organizations of the weld and base metal of the match.
Post time: Mar-13-2020